Re: is ErrorResponse possible on Sync?

From: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
To: Andrei Matei <andreimatei1(at)gmail(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: is ErrorResponse possible on Sync?
Date: 2022-01-12 19:39:20
Message-ID: 202201121939.zrszuiavtgy4@alvherre.pgsql
Views: Raw Message | Whole Thread | Download mbox | Resend email
Lists: pgsql-hackers

On 2022-Jan-12, Andrei Matei wrote:

> If Sync itself cannot fail, then what is this
> sentence really saying: "This parameterless message (ed. Sync) causes the
> backend to close the current transaction if it's not inside a BEGIN/COMMIT
> transaction block (“close” meaning to commit if no error, or roll back if
> error)." ?
> This seems to say that, outside of BEGIN/END, the transaction is committed
> at Sync time (i.e. if the Sync is never sent, nothing is committed).
> Presumably, committing a transaction can fail even if no
> previous command/statement failed, right?

A deferred trigger can cause a failure at COMMIT time for which no
previous error was reported.

alvherre=# create table t (a int unique deferrable initially deferred);
alvherre=# insert into t values (1);
alvherre=# begin;
alvherre=*# insert into t values (1);
alvherre=*# commit;
ERROR: duplicate key value violates unique constraint "t_a_key"
DETALLE: Key (a)=(1) already exists.

I'm not sure if you can cause this to explode with just a Sync message, though.

Álvaro Herrera Valdivia, Chile —

In response to


Browse pgsql-hackers by date

  From Date Subject
Next Message Andrew Dunstan 2022-01-12 19:54:13 Re: support for MERGE
Previous Message Andrew Dunstan 2022-01-12 19:34:00 Windows vs recovery tests